Listen to Robert Emmerich introduce The Big Apple, a hit song from 1937. Music written by Bob and performed by Tommy Dorsey's Clambake Seven with Bob on piano. Lyrics written by Buddy Bernier and sung by Edythe Wright. Audio provided by Dorothy Emmerich.

A “blue collar” worker is someone of the working class, such as a tradesperson. A “white collar” worker is a professional or educated worker, or someone who works in an office. The term “blue collar jobs” has been cited in print since at least 1924. The origin of “blue collar” is uncertain; it was probably used to contrast with the earlier “white collar” term. Many tradesmen of the 1920s and 1930s did wear blue collars, but the blue collar didn’t have nearly the popularity and uniformity of use as the white collar had.

The term “white collar” (job or worker) has been cited in print since at least 1910.

Wikipedia: Blue-collar worker
A blue-collar worker is a member of the working class who typically performs manual labor and earns an hourly wage. Blue-collar workers are distinguished from those in the service sector and from white-collar workers, whose jobs are not considered manual labor.

Blue-collar work may be skilled or unskilled, and may involve manufacturing, mining, building and construction trades, mechanical work, maintenance, repair and operations maintenance or technical installations. The white-collar worker, by contrast, performs non-manual labor often in an office; and the service industry worker performs labor involving customer interaction, entertainment, retail and outside sales, and the like.

Origin of the term
The term blue-collar is derived from 19th century uniform dress codes of industrial workplaces. Industrial and manual workers wear durable clothing that can be dirty, soiled, or scrapped at work. A popular element of such clothes has been, and still is, a light or navy blue work shirt. Blue is also a popular color for coveralls, and will frequently include a name tag of the company/establishment on one side, and the individual’s name on the other. Often these items are bought by the company and laundered by the establishment as well.

The popularity of the color blue among manual laborers is in contrast to the ubiquitous white dress shirt that is standard attire in office environments. Color-coding has been used to identify a difference in socio-economic class. This distinction is becoming more blurred, however, with the increasing importance of skilled labor, and the growth of non-laboring, but low-paying, service sector jobs. “Blue-collar” may also be used as an adjective to describe the environment of the blue-collar worker: a “blue-collar” neighborhood, job, restaurant, bar; or any situation describing the use of manual effort and the strength required to do so.

Education requirements
A distinctive element of blue-collar work is the lesser requirement for formal academic education which is needed to succeed in other types of work, with many blue-collar jobs requiring only a high school diploma or (in the USA and Canada) GED. Blue-collar work typically is hourly wage-labor. Usually, the pay for such occupation is lower than that of the white-collar worker, although higher than many entry-level service occupations. Especially skilled blue-collar jobs may pay very well compared to white collar jobs. Sometimes the work conditions can be strenuous or hazardous, also known as the three Ds: Dirty, Demanding, and Dangerous. Blue collar jobs may be represented by trade unions or regulated by state and/or federal statutes.

(Oxford English Dictionary)
blue-collar attrib. (chiefly U.S.), designating a manual or industrial worker, as distinct from a ‘white-collar’ worker
1950 Tuscaloosa News 25 Nov. 1/5 ‘*Blue collar’ workers also include helpers, laborers, and supervisors.
1958 Listener 23 Oct. 631/1 The blue-collar people, the machine operators.
1959 Observer 1 Nov. 8/2 The split is no longer between white- and blue-collar workers, but between those with and those without the college diplomas.

14 May 1929, The Southwest Times (Pulaski, VA), “Correcting Mr. Crawford” (editorial), pg. 4, col. 1:
The Times is for organized labor because it believes that this is the only way that the blue collar man can command decent, living wages, reasonable hours and the proper working conditions.

6 October 1933, Richmond (VA) Times-Dispatch, “Urges NRA Support,” pg. 12, col. 6:
In some sections of the country unemployment among the white collar workers is increasing, but amongst the blue collar and hickory shirt workers unemployment is on the decrease.
(...)
W. L. SCOTT.
Burlington, N.C.

Google News Archive
19 August 1934, Pittsburgh (PA) Press, Society Section, pg. 11, col. 1:
The attack having the most prominent position, however, in the public eye is the one exhibited through the “share-the-work” plan or “stagger system” or employment, which compelled nearly all white collar and blue collar workers to shoulder the economic burden created by the blundering, asinine, stupid methods of industrialists and their governmental puppets.

Google News Archive
14 October 1934, Pittsburgh (PA) Press, “A 30-Hour Week Is Necessary, He Says,” Society Section, pg. 13, col. 6:
Despite this undeniably obvious fact, however, industrialists continue sitting before the Wall Street spinning wheel (capitalism) and spin organized thoughts of greed by trying to get more and more service out of their white and blue collar workers—through an intensified “stagger” and “speed up” system—for less and less outlay, thus lowering the buying power of the masses and spragging the wheels of the industrial machine.
(...)
ROBERT F. MARTIN.
Martins Ferry, O.

Google News Archive
1 October 1935, Pittsburgh (PA) Press, pg. 2, col. 8:
The News—Dr. Howard W. Haggard and Leon A. Greenberg of Yale University have come to the conclusion that five meals instead of the customary three would be more beneficial to workers—white collar and blue collar.

Google News Archive
29 December 1935, Pittsburgh (PA) Press, “Battle Front Is Ballot Box,” society section, pg. 11, col. 1:
The “system” and all those who have faith in and support it are our foes; whether white collar or blue collar, rich or poor.

Dr. F. Theodore Struck, head of Penn State’s department of industrial education, points out that at present twice as many public school pupils desire to enter the professions and technical fields as these vocations may reasonably be expected to absorb.

7 June 1942, Rockford (IL) Morning Star, pg. 8, col. 4 ad:
For here is a war EVERYBODY is in. The man behind the plow. The kid in knee pants. The oldster with the cane. The housewife with the market basket. The white-collar worker. The blue-collar worker. The girl in the schoolroom.
("Buy More Bonds”—ed.)

15 July 1945, New York (NY) Times, “Labor Corrections at Navy Yard Urged,” pg. 15:
Simplification of the efficiency rating system for “blue collar workers” to make it more easily understood by employes.

6 April 1949, Dallas (TX) Morning News, sec. 1, pg. 16:
“Blue Collar”
Workers Lead
In U.S. Group
Two out of every three civilian employees of the Federal Government in Texas work for either the army, navy, Air Force or post office.

Three out of every four work for the armed services, the post office or the Veterans Administration.

Most federal employees in Texas are “blue collar,” rather than “white collar” workers—that is, mechanics and craftsmen, rather than office workers.